The cTnT response to acute exercise at the onset of an endurance training program: evidence of exercise preconditioning?

PurposeExercise induces a cardioprotective effect referred to as preconditioning. Whether the preconditioning impacts upon the cardiac troponin T (cTnT) response to subsequent exercise bouts is unclear. This study investigated the effects of an initial exercise bout, a second exercise bout 48h later, as well as subsequent exercise every 48h for 4 days or a single identical exercise bout after 8 days of inactivity gap on cTnT response to acute exercise.MethodsTwenty-eight sedentary overweight young women were randomly assigned to either six bouts of exercise each separated by 48h or three bouts of exercise with 48h between the first two bouts and 8 days between the second and third bouts. All exercise bouts were identical (60% VO2max, 200kJ) and the total testing period (10 days) was the same for both groups. cTnT was assessed before and after the 1st, 2nd, and final exercise bouts.ResultscTnT increased (129%, P<0.05) after the first bout of exercise in both groups (peak post-exercise cTnT, median [range], ngl(-1): 3.43[<3.00-27.26]) with no between-group differences in the response. The second exercise bout had no significant (P>0.05) effect on post-exercise cTnT (<3.00[<3.00-21.96]). The final exercise bout resulted in an increase (190%, P<0.05) in cTnT (4.35[<3.00-13.05]) in both groups.ConclusionsA single bout exercise resulted in a temporary blunting of cTnT response to acute exercise 48h later. The effect of exercise preconditioning was not preserved, regardless of whether followed by repeated exercise every 48h or a cessation of exercise for 8 days.